Use of Allele-Specific-Amplification Refractory Mutation System–Polymerase Chain Reaction for the Detection of Thyroid-Stimulating Hormone Receptor Gene Mutation in an Indian Family with Thyroid Dyshormonogenesis

The frequency of thyroid-stimulating hormone receptor (TSHR) gene variant c.1349G>T, p.arginine[R]450leucine[L] in the Asian population has been reported to be high. However, the whole exome sequencing (WES) performed using our samples could not detect this mutation. Moreover, the clinical utility of allele-specific (AS)-amplification refractory mutation system (ARMS)–polymerase chain reaction (PCR) has not been explored in the detection of TSHR gene mutation c.1349G>T, p.R450L in cases with thyroid dyshormonogenesis (TDH). Therefore, we aim to investigate the inheritance and TSHR gene mutation c.1349G>T, p.R450L in an Indian child with TDH and his biological parents. At present, the mutation analysis of TDH-causing genes like dual oxidase (DUOX2) [c.3200C>T, p.Ser(S)1067L] and thyroid peroxidase (TPO) [c.404C>A, p.Pro(P)135His(H)] by WES and TSHR gene variant c.1349G>T/p.R450L by AS-ARMS-PCR was performed. Three years and 1 month-old male child born to nonconsanguineous parents presented with constipation and prolonged indirect hyperbilirubinemia at 1.5 months of age. The evaluation revealed a very high level of serum thyroid stimulating hormone and a low level of free thyroxine (fT4) and fT3. The technetium99 scan showed increased tracer uptake in the thyroid gland. Out of 131 variants identified in TDH-causing genes by WES, DUOX2 gene variant c.3200C>T, p.S1067L and TPO gene variant c.404C>A, p.P135H were noticed to be clinically associated with TDH. Applying AS-ARMS-PCR for the first time, we report the whole Indian family carrying an autosomal heterozygous variant (c.1349G>T/p.R450L) in the hotspot mutation region of the TSHR gene. In conclusion, the known TSHR gene variant c.1349G>T/p.R450L (an autosomal heterozygous), and other variants of the DUOX2 gene (c.3200C>T, p.S1067L) and TPO gene (c.404C>A, p.P135H) might contribute to clinically more severe TDH in children born to carrier parents. We recommend a large-scale study and confirmation of the mutations by Sanger sequencing.